Squeezed light (also referred to light in a squeezed state) refers to light in which the electric field strength for some phases has a quantum uncertainty (also referred to as noise) smaller than that of a coherent state. A wide range of applications can benefit from high quality sources of squeezed light. For example, in metrology, using squeezed light allows certain optical sensors to overcome the shot noise limit and achieve sensitivities many times higher than possible with conventional light sources. In quantum communications, squeezed light can be used to distribute entanglement, thereby assisting cryptographic key distribution protocols. Squeezed light sources can also be used to deterministically generate massive highly entangled quantum states, enabling the construction of scalable quantum simulation and computation devices operating in the optical domain using a continuous variable (CV) encoding.
To fully exploit the potential of squeezed light in above applications, it is desirable for the squeezed light source to be scalable, tunable, compatible with existing optical technology including single photon detection, and capable of generating controllable temporal mode structures in the output. To date, however, no known squeezed light source can achieve all these goals at the same time. For example, squeezed light sources based on parametric down-conversion in bulk non-centrosymmetric crystals are compatible with single photon detection, but it is challenging to control the temporal mode structure of their output. In addition, this method is not scalable because it relies on bulk optical elements that are difficult to stabilize. Squeezed light sources based on the Kerr effect in nonlinear fiber are compatible with 1550 nm operation. But it is incompatible with single photon detection and usually produces a very complex temporal mode structure.